This project will investigate immunoregulation of the T cell-mediated immune response of contact hypersensitivity of 1-fluoro-2,4-dinitrobenzene (DNFB) in mice. Tolerance induced by the i.v. injection of hapten-modified lymphoid cells (hapten-LC) is mediated by two separate pathways - clone inhibition and antigen-specific suppressor T cells (Ts). Genetic restrictions on both Ts induction and expression will be investigated using hapten-LC labeled with both high and low epitope density hapten concentrations. Ts active on both afferent (induction) and efferent (elicitation) phase of the response will be examined as to their cellular target - i.e., T helper, pre- or mature delayed hypersensitivity effector cells. Also, mechanisms and genetic restrictions of T-T interactions between Ts and Ts auxiliary cells in efferent suppression will be studied. Finally, the effects of i.v. tolerization with hapten-LC and soluble hapten on the development of anti-hapten-modified self cytotoxic cells will be examined.